1. Field of the Invention
The present invention relates to an optical head device as an optical system component of an optical disc apparatus which reads or writes information from/to an optical disc, more particularly, to a preferred optical head device suitable for reducing size (thickness) of the optical disc device.
2. Description of the Related Art
In a field of the optical disc apparatus, that of a thinner structure is desired as a drive to be embedded in a compact personal computer such as a laptop personal computer. Consequently, as the optical head device to be embedded in the laptop personal computer, the structure of the optical head device is virtually limited to the one constituted with an object lens opposed to an optical disc (media), above and very close thereto a mirror which bends an optical path at 90 degree, opposed to the mirror a collimator lens, and opposed to the collimator lens a light-emitting element or a light detecting element. It is because without the mirror an optical system becomes long to a normal direction of a media surface and hampers reducing thickness. The optical system including the mirror is mounted on a member called an optical base, and constituted integrally.
Here, the object lens of the optical head device is required to be displaced, for the purpose of tracking, in a radial direction of the media, following a track on the media, and is further required to be displaced also in a normal direction of the media or in a direction around a rolling axis, following a warp or a tilt of the media. As a result, an actuator displacing the object lens in each direction is required very close thereto. In order to equip the actuator without hampering miniaturization, a shape of the optical base is often a frame, and an inside of this frame (opening) is provided as an area in which the actuator is positioned. Consequently, the optical head device miniaturized as a whole is available.
The actuator mounted within the opening of the optical base, on the other hand, becomes a source to bring the optical base a deformation (bend or torsion) by a vibration. Such a deformation becomes an obstacle for the optical system to soundly exert its function. In particular, when faster writing (for example, 24 times speed for a CD, 8 times speed for a DVD) comes to be required of the optical disc device, an operation speed of the actuator becomes faster, relatively increasing a side effect as being an unnecessary vibratory source.
At present, it is difficult to simultaneously pursuit reducing size/thickness and increasing stiffness of the optical base, and some solution is desired. Incidentally, an example of the structure of the optical head device is described in the following patent document 1. In this example, the actuator is mounted on the optical base without an inside frame area and ultimate reduction of thickness is not achieved.    [Patent document 1] Japanese Patent Laid-open Application No.2002-312963